This invention relates generally to a control system of the type wherein manual control devices such as a control stick or hand controller are provided which have an electro simulated variable rate feel. These hand controllers use a torque loop with proportional and integral control to achieve the required force-displacement characteristic of the hand grip. Hand controller systems having this electro simulated variable rate feel are commonly referred to as active hand controller systems. Hand controller systems are described in issued U.S. Pat. No. 5,264,768 having an issue date of Nov. 23, 1993 and issued U.S. Pat. No. 5,291,113 having and issue date of Mar. 1, 1994 which are hereby incorporated by reference.
The related inventions referenced hereinbefore utilize electric motors to produce desired hand controller force and position response. These systems require sensors which can provide force and position signals.
Aircraft and spacecraft flight control systems have a critical role in flight safety and therefore have stringent performance and reliability requirements. Systems are designed to be fault tolerant, i.e., the system can continue to operate with a fault. Fault tolerant systems can be designed using a parallel reliability concept so that in the event of the failure of a single component a duplicate or paralleled component takes over the function of the failed component. Electronic subsystems or modules are routinely provided in redundant parallel arrangements. Many aircraft flight control systems are designed to provide four parallel modules for quadruple redundancy. In active hand controller systems, for various reasons, it is not practical to provide four motors for each axis of a hand controller. However commercial aircraft include a separate hand controller or sidestick for each of the pilot and copilot. If each of the sidesticks are provided with two motors coupled to a common shaft per each axis, then a form of quadruple redundancy has been provided.
Integral control acts such that the feedback error signal is integrated to generate a command which corrects the error signal to a null condition. In an active hand controller the feedback error signal is corrected by a motor applying torque to a shaft which is configured to apply a force to a hand grip. In a redundant hand controller two motors are configured to apply a torque to one shaft. Redundant integral controllers receive two separate feedback error signals that are separately integrated. This results in two separate motor command signals which are applied to the two motors connected to a common motor shaft. Both integrators will not be capable of nulling their individual error signals simultaneously due to slight variations in each redundant path. Hence, one of the integrators will ramp-off, or oscillations will result between the redundant motors.
Thus a need exists for an integration management system that allows both motors to operate at a null condition.